The present invention relates to a metallic-conduit-armored type linear member wherein a linear member such as an optical fiber or an electrical wire, and in some cases a filler material such as a water sealing compound in addition to the linear member, are accommodated in a metallic conduit, a metallic conduit for armoring the linear member, and a method and a system for manufacturing the metallic-conduit-armored type linear member. More particularly, the present invention concerns a metallic-conduit-armored type linear member in which an outer surface of a metallic conduit is coated with metal, a metallic conduit for armoring the linear member, and a method and a system for manufacturing the metallic-conduit-armored type linear member.
A linear member armored by a metallic conduit is well known as a cable which can be used even in a hostile environment since the metallic conduit is capable of ensuring mechanical strength and environmental resistance. In the case of the metallic-conduit-armored type linear member disclosed in Japanese Patent Examined Publication No. 10805/1988, an optical fiber 51, which is the linear member, is accommodated in a metallic conduit 52 as a metallic-conduit-armored type linear member 50 shown in the appended FIG. 4. Such a metallic-conduit-armored type linear member shown in FIG. 4 is used singly or as an element of a composite cable, such as the one shown in FIG. 5, in which other cables or tension members 54 are disposed around it. As one method of manufacturing such a metallic-conduit-armored type linear member, a technique is known in which the extra length of the linear member with respect to the length of the metallic conduit is arbitrarily adjusted to positive, zero, or negative in accordance with the working environment (e.g., Japanese Patent No. 2,505,336). Here, the extra length refers to the difference in the length of the linear member with respect to the metallic conduit, and if the linear member is longer, the extra length is called positive extra length, whereas if the metallic conduit is longer, it is called negative extra length. It should be noted that the ratio of the extra length to the length of the metallic conduit is sometimes referred to as the extra length ratio.
A typical example of secondary processing for imparting an additional function to the metallic-conduit-armored type linear member is the formation of a metallic coating layer on the surface of the armoring metallic conduit (see a metallic coating layer 53 in FIG. 4, for example). This metallic coating layer further improves the mechanical strength and environmental resistance which are the functions of the metallic conduit itself. Particularly with respect to the latter, by adopting an appropriate coating metal in the case shown in FIG. 5, for example, it becomes possible to prevent electric corrosion due to the difference in the ionization tendency with respect to the metal constituting the cables or tension members 54 surrounding the metallic-conduit-armored type linear member 50. For example, Japanese Patent Unexamined Publication No. 69,716/1996 discloses a twisted assembly including tension members in which corrosion resistance is enhanced by forming a 5 to 70 xcexcm-thick aluminum coating layer on the surface of an armoring metallic conduit.
As a typical example of the technique for forming such a metallic coating layer on the outer surface of a metallic conduit, the aforementioned Japanese Patent Examined Publication No. 10,805/1988 can be cited. In this example, as shown in FIG. 6, a metallic tape 55A fed out from a tape supply 55 is formed into a tubular shape in a pipe forming step 57, in which step an optical fiber 56A is also concurrently supplied from a fiber supply 56, thereby forming an optical-fiber-accommodating metallic pipe 58. Subsequently, after the seam of this pipe 58 is welded in a welding step 59, the metallic coating layer 53 formed of, for example, aluminum is provided on the outer surface of the metallic pipe 58 by means of vacuum plating such as vacuum deposition, sputtering, ion plating, or the like in a plating step 60. The vacuum plating is performed continuously with respect to the metallic pipe for which welding has been completed, and the plated metallic pipe is taken off by a takeoff 61 and is taken up by a takeup 62.
In addition, in Japanese Patent Unexamined Publication No. 2,909/1985, a metallic tape is formed into a tubular shape, and an optical fiber is concurrently supplied to form an optical-fiber-accommodated metallic pipe, and this pipe is immersed in a molten metal bath so as to weld the seam of the metallic pipe and provide a metallic coating layer on the outer surface of the metallic pipe. Further, in the aforementioned Japanese Patent Unexamined Publication No. 69,716/1996, a metallic layer is provided on the outer surface of an armoring metallic pipe in a sintering process or by a chemical or electrochemical method.
However, the following problems are encountered with the conventional techniques. The first problem is that of the thermal effect. As also pointed out in Japanese Patent Unexamined Publication No. 2,909/1985, in a case where the metallic coating layer is formed on the outer surface of the metallic conduit, the fact that the linear member in the metallic conduit receives a thermally adverse effect presents a large problem, and it does not follow that such a thermally adverse effect can be allowed in light of quality assurance just because the coating layer of the optical fiber is apparently not subjected to thermal damage. Particularly in the case where the linear member is a thermally sensitive substance typified by the optical fiber and in the case where a space filler such as a water sealing compound other than the linear member is filled in the metallic conduit, it can hardly be denied that the provision of vacuum plating without adopting some heating preventing means is very dangerous processing which directly leads to the degradation of the quality of the metallic-conduit-armored type linear member. Particularly in a case where it is necessary to form a thick metallic coating layer with a thickness of not several microns or thereabouts but as much as 10 microns or more, surface treatment must be generally effected for a relatively long time, and the possibility of the thermally adverse effect on the substances which are present in the metallic conduit becomes substantially high.
In addition, the thermally adverse effect during the formation of the coating on the metallic conduit surface is also exerted on the metallic conduit itself. Namely, there is a possibility that defective welds which originally existed are further expanded by the thermal expansion of the metallic conduit itself and the thermal shock acting on the metallic conduit, giving rise to new defective joined portions. In the case where a space filler material such as a water sealing compound is contained in the sealed metallic conduit, there increases the possibility that the thermally expanded space filler material jets out from such defective joined portions. Furthermore, even in a case where such a space filler is not present or in a case where a thermally sensitive substance such as the optical fiber is inserted in the armoring metallic conduit after the formation of the metallic coating, the presence or generation, per se, of the defective welds in the metallic conduit constitutes a major problem in terms of the product quality of the metallic-conduit-armored type linear member. In addition, if the plating bath infiltrates into the interior through the defective welds and then solidifies, there is a possibility of causing trouble to the subsequent loading of the linear member and the space filler material. The foregoing problems become no longer negligible in a case where a thick metallic coating layer with a thickness of as much as 10 microns or more is formed on the metallic conduit or in a case where the metallic-conduit-armored type linear member is exposed under a thermal effect for a longer period of time. To solve these problems, a perfect welding technique is required. However, a perfect welding technique as such does not exist.
If the conventional techniques are considered from such a perspective, in the aforementioned Japanese Patent Examined Publication No. 10,805/1988 there is a teaching that the metallic pipe does not assume a high temperature if the metallic coating layer is formed by vacuum plating, and the coating layer of the optical fiber is therefore not subjected to thermal damage; however, there are cases where the assertion that the plated material does not assume a high temperature by vacuum plating is contrary to the fact. In the case of the aforementioned Japanese Patent Unexamined Publication No. 69,716/1996 only an enumeration is given of known film forming techniques including sintering or chemical or electrochemical means, and there are no teachings concerning how the thermal effect, i.e., the realistic problem of product quality, is solved.
In the final analysis, the surface treatment techniques concerning the metallic conduit for armoring the linear member must have a small thermal effect. However, that alone is insufficient in practice. It is necessary to select an optimum surface treatment technique concerned after taking into consideration the features of the metallic-conduit-armored type linear member and its manufacture.
Secondly, in the plating apparatus in Japanese Patent Unexamined Publication No. 81,191/1994, in the same way as ordinary plating apparatuses for linear members (refer to, for example, Japanese Patent Unexamined Publication Nos. 132,797/1993 and 39,594/1993, Japanese Utility Model Unexamined Publication No. 37,366/1984, Japanese Patent Unexamined Publication No. 117,243/1977, and Japanese Patent Examined Publication No. 23,756/1982), the traveling direction of the member subject to treatment is changed greatly a plurality of times in the process of plating treatment, so that the metallic conduit containing the optical fiber is subjected to virtual mechanical processing. Such mechanical processing also occurs when the member to be treated which is wound around an accommodating device such as a bobbin is unwound for plating treatment or when the member is wound again around the accommodating device after completion of plating. If such mechanical processing is applied to the metallic-conduit-armored type linear member, the metallic conduit shrinks in its longitudinal direction (refer to, for example, Japanese Patent Unexamined Publication Nos. 55,804/1992 and 19,153/1993), and the extra length (positive extra length) increases more than an initial target value. Accordingly, when the surface of the armoring metallic conduit is provided with a metallic coating, special consideration which takes into account such variations in the extra length is required in product quality control.
Thirdly, if mechanical processing is repeatedly provided for the metallic conduit in the plating process, there is a possibility that defective welds at sealed portions are expanded or new defective welds are produced. A similar result is also produced by the thermally adverse effect during the formation of a coating on the metallic conduit, as described above. If defective welds in the metallic conduit remain, the technique of continuously providing a metallic coating on the metallic conduit by the vacuum plating process disclosed in the aforementioned Japanese Patent Examined Publication No. 10,805/1988 is incapable of pressure reduction, and therefore becomes unrealizable. Also, defective welding becomes an issue in a case where the metallic conduit containing the linear member and the space filler is electrochemically formed in an electrolyte atmosphere. Namely, the plating solution enters the interior of the metallic conduit through defective welds, and the reaction with the plating solution takes place inside the metallic conduit as well, causing a decline in the quality of the metallic-conduit-armored type linear member. For this reason, even in cases where the metallic conduit surface is electrochemically treated, special consideration is required with respect to the defective welding of the metallic conduit.
The present invention has been devised in view of the above-described aspects, and its object is to provide a metallic-conduit-armored type linear member in which an outer surface of a metallic conduit is provided with a metallic coating, a metallic conduit for armoring the linear member, and a method and a system for manufacturing the metallic-conduit-armored type linear member.
The above object is attained by a first aspect of the invention concerning a linear member which is armored by a metallic conduit having a metallic coating layer formed thereon by plating treatment which is effected by using a room-temperature molten-salt electrolytic bath, and by a second aspect of the invention concerning a metallic conduit for a metallic-conduit-armored type linear member having a metallic coating layer formed thereon by plating treatment which is effected by using a room-temperature molten-salt electrolytic bath.
In addition, the above object is also attained by a third aspect of the invention concerning a method of manufacturing a metallic-conduit-armored type linear member having a metallic conduit on an outer surface of which a metallic coating layer is formed by plating treatment which is effected by using a room-temperature molten-salt electrolytic bath. In this third aspect of the invention, the metallic conduit may be formed of copper, a copper alloy, or stainless steel, and the metallic coating layer may be formed of aluminum. In addition, the room-temperature molten-salt electrolytic bath may be an electrolytic bath using an AlCl3-1-butyl pyridinium chloride-based or AlCl3-ethyl-methylimidazolium chloride-based room-temperature molten salt. At that juncture, the electrolytic bath is preferably 80 to 150xc2x0 C., more preferably 80 to 100xc2x0 C.
The above object is also attained by a fourth aspect of the invention concerning a manufacturing method comprising: a basic step of forming a sealed metallic conduit into an interior of which a linear member can be loaded, by forming a metallic tape into a tubular member and by joining a seam of the tubular member; and a metallic coating step of forming a metallic coating layer on an outer surface of the sealed metallic conduit by performing plating by using a room-temperature molten-salt electrolytic bath subsequent to the basic step. In this fourth aspect of the invention, an inspecting step may be further provided between the basic step and the metallic coating step for performing quality inspection of the metallic-conduit-armored type linear member. Further, an extra-length adjusting step may be provided for adjusting the extra length of the linear member with respect to the sealed metallic conduit. This extra-length adjusting step need not be provided in the basic step. The extra-length adjusting step may be provided in the basic step, or the extra length may be adjusted in a line separate from the line for continuously manufacturing the metallic-conduit-armored type linear member.
In addition, the above object is also attained by a fifth aspect of the invention concerning a manufacturing method comprising: a basic step of forming a sealed metallic conduit into an interior of which a linear member can be loaded, by forming a metallic tape into a tubular member and by joining a seam of the tubular member; a metallic coating step of forming a metallic coating layer on an outer surface of the sealed metallic conduit subsequent to the basic step; and an inspecting step provided between the basic step and the metallic coating step for performing quality inspection of the metallic-conduit-armored type linear member. The metallic coating forming technique applicable in this fifth aspect of the invention is not limited to the plating technique using the room-temperature molten-salt electrolytic bath in the third aspect of the invention, and vacuum plating and other known film forming techniques suffice. The basic step, the inspecting step, and the extra-length adjusting step are similar to the case of the fourth aspect of the invention.
Furthermore, the above object is also attained by a sixth aspect of the invention concerning a manufacturing system comprising: a basic processing apparatus for forming a sealed metallic conduit into an interior of which a linear member can be loaded, by forming a metallic tape into a tubular member and by joining a seam of the tubular member; and a metallic coating apparatus for forming a metallic coating layer on an outer surface of the sealed metallic conduit by performing plating by using a room-temperature molten-salt electrolytic bath. In this sixth aspect of the invention, the manufacturing system may further comprise: an inspecting apparatus for performing quality inspection of the metallic-conduit-armored type linear member fabricated by the basic processing apparatus, a repairing apparatus for performing necessary repair with respect to the metallic-conduit-armored type linear member on the basis of the result of inspection, or an extra-length adjusting apparatus for subsequently adjusting the extra length of the linear member with respect to the sealed metallic conduit.
As described above, in accordance with the present invention, since a metallic coating is provided on the outer surface of the armoring metallic conduit by using the room-temperature molten-salt electrolytic bath, it is possible to provide an armoring metallic conduit provided with a metallic coating or a linear member contained in such an armoring metallic conduit, which is not subjected to adverse effects due to heat, moisture, and an organic solvent, and whose yield and quality as a product are high. In addition, in accordance with the manufacturing method and the manufacturing system in accordance with the present invention, by virtue of the metallic coating on the surface of the armoring metallic conduit using the room-temperature molten-salt electrolytic bath, it is possible to overcome various problems which can occur in the subsequent metallic coating treatment owing to the presence of defective welds and/or other causes. Furthermore, since extra-length control is provided by estimating variations in the extra length which occur in the process from the fabrication of the armoring metallic conduit until completion of the metallic coating on the surface of the armoring metallic conduit, it is possible to manufacture a high-quality metallic-conduit-armored type linear member whose extra length is adjusted to a target value.